1. Field of the Invention
The present invention relates to recording thin-film magnetic heads for use in, for example, floating magnetic head devices and their manufacturing methods. In particular, the present invention relates to a thin-film magnetic head that can precisely define tracks having a predetermined width, be properly compatible with narrower tracks, have a shorter magnetic path, and prevent flux leakage to improve the recording characteristics, and its manufacturing method.
2. Description of the Related Art
FIG. 28 is a longitudinal sectional view of a known thin-film magnetic head, where X indicates a track-width direction; Y indicates a height direction of the magnetic head; and Z indicates a traveling direction of the magnetic head over a magnetic recording medium such as a hard disc. The front surface (the leftmost surface in the drawing) of this magnetic head parallel to plane X-Z faces the recording medium.
In FIG. 28, a lower core layer 6, which is made of, for example, Ni—Fe alloy, has a protrusion 6a extending upward (in the Z direction in the drawing) along the front surface of the magnetic head. A back gap layer 7 of a magnetic material is formed on the lower core layer 6 at the rear of the magnetic head in the height direction (in the Y direction in the drawings). The space between the protrusion 6a and the back gap layer 7 on the lower core layer 6 includes some portions of a coil layer 8 of, for example, copper, and is filled with an insulating layer 9. The protrusion 6a, the insulating layer 9, and the back gap layer 7 have flat top surfaces 6b, 9a, and 7a, respectively.
A gap layer 10 of, for example, Al2O3 is formed on the top surfaces 6b and 9a of the protrusion 6a and the insulating layer 9. A nonmagnetic layer 12 is formed on this gap layer 10 away from the front surface of the magnetic head in the height direction by a predetermined distance. An upper magnetic pole layer 11 is further formed over the top surfaces of the gap layer 10, the nonmagnetic layer 12, and the back gap layer 7.
Such a thin-film magnetic head is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2001-319311.
In recent years, smaller thin-film magnetic heads and higher-speed magnetic head devices have been developed with higher recording densities and higher frequency. This trend imposes more severe requirements on thin-film magnetic heads.
In the magnetic head shown in FIG. 28, a seed layer 13 for plating the upper magnetic pole layer 11 is substantially separated into a seed layer 13a formed on the nonmagnetic layer 12 and a seed layer 13b formed on the protrusion 6a of the lower core layer 6. These seed layers 13a and 13b are spaced in the height direction by a distance S.
Smaller magnetic heads demand that the upper magnetic pole layer 11 have a smaller thickness. Unfortunately, if the seed layer 13 is substantially separated, such a thin upper magnetic pole layer 11 cannot be reliably formed on the nonmagnetic layer 12.
Smaller magnetic heads have difficulty in connecting an electrode to the seed layer 13a on the nonmagnetic layer 12 during their formation. Therefore, the electrode is connected to the seed layer 13b on the protrusion 6a to form the upper magnetic pole layer 11 on the seed layer 13b by plating. This upper magnetic pole layer 11 is allowed to grow until it extends over the nonmagnetic layer 12 and reaches the seed layer 13a. 
If the upper magnetic pole layer 11 reaches the seed layer 13a, current can be passed through the seed layer 13a to grow the upper magnetic pole layer 11 entirely over the seed layer 13a. However, if the upper magnetic pole layer 11 has a small thickness, it may fail to reach the seed layer 13a. Then, as shown in FIG. 29, the upper magnetic pole layer 11 cannot be formed over the nonmagnetic layer 12, thus producing a magnetic head that cannot perform magnetic recording or, even if possible, that has significantly poor recording characteristics.
As described above, this magnetic head cannot be properly compatible with higher recording densities and higher frequency in future, nor can it improve the recording characteristics.